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A
AGP
See Advanced Graphics Port
AIMM
AGP inline memory module (See Advanced
Graphics Port)
Access Time
A measurement of time in nanoseconds (ns)
used to indicate the speed of memory. Access
time is a cycle that begins the moment the
CPU sends a request to memory and ends the
moment the CPU receives the data it
requested. Memory modules complete this
process in as fast as 6ns for PC133mhz
memory while older modules can take up to
80ns or more.
Advanced Graphics Port
(Accelerated
Graphics Port) AGP technology creates
dedicated, high-speed port for the
transmission of large blocks of high
resolution data between the PC's graphics
controller and system memory. AGP is
actually a port, and not a bus, because it
only serves two devices (the processor and
the video card) and is not expandable. One
of the great advantages of AGP is that it
isolates the video subsystem from the rest
of the PC so there isn't nearly as much
signal competition over I/O bandwidth as
there is across the PCI.
Asynchronous Cache
Describes a
type of L2 cache that is not in synch with
the system clock. Asynchronous cache is
slower than its synchronous counterpart, but
is capable of delivering information to the
CPU at a rate 10 percent faster than
standard DRAM. Asynchronous cache was first
used to boost memory performance in 386
systems and is still widely used today.
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B
BEDO
(Burst EDO) DRAM -- a type
of EDO DRAM that can process four memory
addresses in one burst. Unlike SDRAM,
however, BEDO DRAM can only stay
synchronized with the CPU clock for short
periods (bursts) and it can't keep up with
processors whose buses run faster than 66
MHz. Burst EDO is a variant on EDO DRAM in
which read or write cycles are batched in
bursts of four. Burst EDO bus speeds range
from 40MHz to 66MHz, as opposed to the 33MHz
bus speeds that can be accomplished using
fast page mode or EDO DRAM.
BGA
See Ball Grid Array
Binary
A method of encoding numbers as a series of
bits. The binary number system, also
referred to as base 2, uses combinations of
only two digits - 1 and 0.
Bit
Short for binary digit, the smallest unit of
data that can be processed or stored by a
computer. A bit can have a value of either 1
or 0. Bits make up 'computer' language the
same way letters of an alphabet make up
human languages. Different combinations of
different bits form 'words' and 'sentences'
(actually signals) that a computer
understands. Before these words and
sentences can be transmitted from the CPU to
memory, or vice versa, they must be broken
down into 8-bit segments called bytes. Older
computers were designed to handle only 8-bit
data segments, while newer models have
progressed to 64-bit segments. This larger
bit width capacity generally means better
and faster computer performance.
BIOS
(Basic Input/Output System)
The BIOS is embedded software that permits a
computer to perform various functions
without accessing code from a hard drive or
other peripheral memory. The BIOS is a main
link between a computer's hardware and
software.
Ball Grid Array
(Ball Grid Array) BGA is a surface-mount
integrated circuit package in which the die
is attached to the printed circuit board
with either plastic or ceramic solder balls
instead of metal leads that are used in
other packaging. BGAs offer superior
electrical and thermal performance and have
a smaller footprint than leaded packages.
Bank
The region on a motherboard
where the slots for memory modules are
located. Memory banks are generally
double-sided to accommodate single or
doubled-sided memory modules.
Block
A collection of data information
held on a storage device. The amount of data
a block contains is usually measured in
bytes.
Buffered Memory
Buffered means adding logic, particularly
drivers, to a SIMM or DIMM to increase the
output current. Buffering is used to
overcome signal attenuation due to
capacitive loading. Modules that are
"buffered" usually have small buffer chips
mounted on them.
Burn-in
The process of exercising an
integrated circuit at elevated voltage and
temperature. This process accelerates
failures normally seen as "infant mortality"
in a chip. (Those chips that would fail
early during actual usage will fail during
burn-in. Those that pass have a life
expectancy much greater than that required
for normal usage.)
Burst Mode
Bursting is a rapid data-transfer technique
that automatically generates a block of data
(a series of consecutive addresses) every
time the processor requests a single
address. The assumption is that the next
data-address the processor will request will
be sequential to the previous one. Bursting
can be applied both to read operations (from
memory) and write operations (to memory).
Bus
The central communication
avenue in a PCs system board. It normally
consists of a set of parallel wires or
signal traces that connect the CPU, the
memory, all input/output devices, and
peripherals and allows data to be
transferred from one system component to
another. Busses come in a variety of bit
widths and speeds. To prevent data
bottlenecks, the components attached to a
bus must operate at close to the same speed
as the bus.
Byte
A unit of information made up of 8
bits. The byte is the fundamental unit of
computer processing; almost all aspects of a
computer's performance and specifications
are measured in bytes or multiples of bytes
such as kilobytes (~1,000 bytes) or
megabytes (~1 million bytes), or gigabytes
(~ 1 billion bytes)
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C
Cache Controller
The circuit in
control of the interface between the CPU,
cache and DRAM (main memory).
Cache memory
Cache RAM is high-speed
memory (usually SRAM) which is dedicated to
storing frequently requested data. If the
CPU needs data, it will check in the
high-speed cache memory first before looking
in the slower main memory. Cache memory may
be three to five times faster than system
DRAM. Most computers have two separate
memory caches; L1 cache, located on the CPU,
and L2 cache, located between the CPU and
DRAM. L1 cache is faster than L2, and is the
first place the CPU looks for its data. If
data is not found in L1 cache, the search
continues with L2 cache, and then on to
DRAM.
Card Memory
A
type of memory typically used in laptop and
notebook computers. Credit card memory
features a small for factor and is named for
its similarity to the size of credit card.
CAS
(Column Address Select/or Strobe)--A
control pin on a DRAM used to and activate a
column address. The column selected on a
DRAM is determined by the data present at
the address pins when CAS becomes active
CAS-B4-RAS (CBR)
(CAS Before RAS)- a
fast refresh technique in which the DRAM
keeps track of the next row it needs to
refresh, thus simplifying what a system
would have to do to refresh the part. CAS
before RAS. Column address strobe before row
address strobe.
CAS Latency
The ratio between column access time and
clock cycle time. CAS Latency 2 (CL2) offers
a slight performance increase over CAS
Latency 3 (CL3).
Check Bits
Extra data bits provided by a
DRAM module to support ECC function. For a
4-byte bus, 7 or 8 check bits are needed to
implement ECC, resulting in a total bus
width of 39 or 40 bits. On an 8-byte bus, 8
additional bits are required, resulting in a
bus width of 72 bits.
Check board
A detail test pattern
designed to exercise each individual cell in
the memory and find possible shorts between
adjacent columns and data buses
Clock
An electrical current that
alternates between high and low voltages.
The speed of the clock is measured in
Megahertz (MHz)
Clock Speed
The rate at which a computer's internal
system clock operates. The clock is used to
synchronize operations between the
components within the clock.
CMOS
Complementary Metal Oxide
Semiconductor: a process that uses both N-
and P-channel devices in a complimentary
fashion to achieve small geometries and low
power consumption.
COAST
(Cache on a Stick) COAST is a module with
SRAM chips that is placed in the CELP socket
on the motherboard to upgrade the computer's
L2 cache.
CPU
(Central
Processing Unit)--The chip in a computer
that has primary responsibility for
interpreting commands and running programs.
The CPU is the most vital component of a
computer system. The speed of the CPU has a
significant impact on overall system
performance, but the CPU doesn't act alone.
If slower memory is paired with a fast
processor, the processor will be forced to
wait for the memory to respond. When the
speed mismatch is extreme, the user will see
numerous memory errors and even complete
system failure.
C-RIMMTM
See Continuity RIMMTM
CSP
See Chip Scale Package.
Chip Set
A group of integrated circuits designed to
carry out one or more related functions of a
computer system. For example, one chipset
may control the flow of peripheral memory
while another governs the system's CPU
functions for the system.
Contacts
See Edge Contacts
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D
DDR
(Double Data Rate) or DDR SDRAM The next
generation of the current SDRAM. DDR finds
its foundations on the same design core of
SDRAM, yet adds advances to enhance its
speed capabilities. As a result, DDR allows
data to be read on both the rising and the
falling edge of the clock, delivering twice
the bandwidth of standard SDRAMS. DDR
essentially doubles the memory speed from
SDRAMs without increasing the clock
frequency.
DIMM
(Dual In-line Memory Module) A
printed circuit board with gold or tin/lead
contacts and memory devices. A DIMM is
similar to a SIMM, but with this primary
difference: unlike the leads on either side
of a SIMM, which are "tied together"
electrically, the leads on either side of a
DIMM are electrically independent, ie
actually separate circuits which allows for
wider and faster data transfer.
DRAM
(Dynamic Random Access
Memory) DRAM is the most common type of
memory and is "dynamic" because in order for
the memory chip to retain data, it must be
refreshed constantly (every few
milliseconds). If the cell is not refreshed,
the data is lost. DRAM temporarily stores
data in a cell composed of a capacitor and a
transistor. Each cell contains a specified
number of bits. These cells are accessed by
row addresses and column addresses.
DRDRAM
(Direct Rambus DRAM)-- a
totally new RAM architecture, complete with
bus mastering (the Rambus Channel Master)
and a new pathway (the Rambus Channel)
between memory devices (the Rambus Channel
Slaves). A single Rambus Channel has the
potential to reach 500MBps in burst mode; a
20-fold increase over DRAM.
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E
ECC
(Error Checking/ Correcting Code) A method
used to check the integrity of data stored
in memory . ECC memory improves data
integrity by detecting errors in memory and
is more advanced than parity because it can
detect both multiple-bit errors and
single-bit errors (parity only detects
single-bit errors). ECC is typically found
in high-end PCs and file servers where data
integrity is key. An ECC scheme capability
is partially determined by the
sophistication of the "systematic code"
employed. The systematic code is like a
reference table that the memory system uses
to determine whether or not the memory has
returned the correct data. Every time data
is stored in memory, this code is
responsible for the generation of check bits
which are stored along with the data. When
the contents of a memory location is
referenced, the ECC memory logic uses the
check bit information and the data itself to
generate a series of "syndrome bits". If
these syndrome bits are all zeros, then the
data is valid and operation continues. If
any bits are ones, then the data has an
error and the ECC memory logic isolates the
errors and reports them in the operating
system. In the case of a correctable error,
the ECC memory scheme can detect single and
double bit errors and correct single bit
errors.
EDO
(Extended
Data Out) EDO RAM is similar to FPM memory,
a form of DRAM technology that shortens the
read cycle between memory and CPU. but
provides improved performance by keeping
available data longer in memory. It
eliminates much of the wait time by allowing
the processor to access data during the
refresh cycle. In other words, the computer
can load data as it is searching for new
information. EDO memory is generally 10 to
20% faster than FPM memory. A computer must
support EDO memory in order to notice an
increase in performance.
EDO
Parity RAM
EDO Parity RAM offers
the high performance of EDO memory and has
built-in parity which greatly improves
reliability. Ideal for high-end PCs and
entry-level servers, EDO Parity modules are
compatible with any system that accepts a
standard 72-pin EDO module and are rapidly
becoming the new standard on high-end
systems.
Edge Contacts
See Edge Connector
Edge Connector
A row of metallic fingers
on the edge of a printed circuit board (PCB)
that is inserted in the appropriate socket
on a motherboard. The edge connector on a
memory module provides the electrical
connection that allows it to communicate
with the system.
EOS
(ECC on SIMM) A data-integrity
checking technology designed by IBM that
features ECC data-integrity checking built
onto a SIMM.
EPROM
Erasable Programmable Read Only
Memory
Ethernet
A
local-area network (LAN) architecture that
enables data transfer rates of 10 Mbps and
can transmit simultaneous demands while
transferring data between several computers.
Even Parity
Even parity and odd
parity are two different parity protocols
used to check the integrity of data stored
in memory. A memory manufacturer can use
either protocol in a memory product. Even
parity adds an additional bit to every byte
of data to make the total number of 1's in
the segment even. When the byte passes to
the CPU, the parity circuit checks the byte
to be sure it is still even. If it is, the
data is considered to be valid and the
parity bit is removed from the byte. If
instead it registers as odd, it is
considered to be invalid and a parity error
is generated.
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F
Fake Parity
Unlike odd and even
parity, fake parity is not capable of
detecting an invalid data bit. It was
designed to artificially 'satisfy' a
parity-enabled computer without actually
checking the data for errors. Fake parity
attaches a bit to each byte of data just
like odd and even parity protocols. The
difference is that fake parity simply adds
the correct parity bit as the data is sent
to the CPU instead of attaching it before
the data is stored to memory, and
recalculating it before the byte passes to
the CPU.
FSB
See Front Side Bus.
Flash
Memory
Flash memory is a
non-volatile memory device that retains its
data when the power is removed. The device
is similar to EPROM with the exception that
it can be electrically erased, whereas an
EPROM must be exposed to ultra-violet light
to erase. Flash memory does not need a
constant power supply to retain its data and
it offers extremely fast access times, low
power consumption, and relative immunity to
severe shock or vibration. These qualities
combined with its compact size, make it
perfect for portable devices like scanners
digital cameras, cell phones, pagers,
handhelds and printers. Flash chips have a
lifespan limited to 100,000 write cycles,
which means flash will never replace main
memory in computers.
FPM
(Fast-Page Mode) A common DRAM
data-access scheme. Accessing DRAM is
similar to finding information in a book.
First, you turn to a particular page, then
you select information from the page.
Fast-page mode enables the CPU to access new
data in half the normal access time, as long
as it is on the same page as the previous
request.
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G
Gb
(see gigabit)
GB
(see
gigabyte)
Gigabit
Abbreviated Gb. Approximately 1
billion bits: 1 bit x 1,024 (that is,
1,073,741,824 bits) Or exactly 2^30 bits.
Gigabyte
Abbreviated GB. A unit
of measurement approximately equal to 1024
megabytes. Computer components process data
in bytes or multiples of bytes such as
kilobytes (~1,000 bytes), megabytes (~1
million bytes), and gigabytes (~ 1 billion
bytes).
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H
HPM
Hyper page mode, also known as EDO.
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I
I/O
Port
(Input/Output) The link
(program or device) that transfers data
between a computer and various peripheral
devices. This traffic can take the form of
in-put only, such as keyboards and mouses,
while printers are generally out-put only.
IC
Integrated Circuit. An
electronic circuit-consisting of components
and connectors-contained on a semiconductor
chip. Usually packaged in a plastic or
ceramic case with external connector pins.
Integrated Circuit.
(see IC)
IO Card
A PCB that interfaces between
the computer and our own interface board.
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J
JEDEC
Joint Electron Device
Engineering Council. An international body
of semiconductor manufacturers that
establishes the industry standards for
memory operation, features, and packaging.
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K
Kilobit
Approximately one thousand bits:
1 bit x 210 (that is, 1,024 bits).
Kilobyte (KB)
A unit of
measurement approximately equal to 1024
bytes. Computer components process data in
bytes or multiples of bytes such as
kilobytes (~1,000 bytes), megabytes (~1
million bytes), and gigabytes (~ 1 billion
bytes).
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L
L1
Cache
(L1 Cache)- Sometimes also
known as primary or level 1 cache, is a
small amount of high-speed memory that
resides on or very close to the CPU. L1
Cache interacts with the CPU for most
frequently requested instructions and data.
L2 Cache
(L2 cache) A specialized
memory unit that enhances DRAM performance
by providing the CPU with data at speeds ten
times faster than DRAM. L2 cache comprised
of Static RAM (SRAM), a high-speed RAM that
does not need to be refreshed to retain its
data. Most computers have two different
memory caches; L1 cache, located on the CPU,
and L2 cache, located between the CPU and
DRAM. L1 cache is faster than L2, and is the
first place the CPU looks for its data. If
data is not found in L1 cache, the search
continues.
Latency
The elapsed time while one
system component waits for output from
another component. Latency is usually
measured in clock cycles.
Logic
Board
(see motherboard)
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M
MB
(see Megabyte)
MHz
(megahertz) represents one million cycles
per second. The speed of microprocessors are
measured in MHz to determine how many
instructions per second it can execute.
MIPS
(million instructions per
second) Measures the amount of system
instructions that a computer can perform in
one second. MIPS ratings are rarely used to
represent system performance due to the fact
that instruction execution times vary and a
mere count of them isn’t an accurate measure
the speed and power of a system.
MTBF
(Mean Time Between Failures)
the average time (usually measured in hours)
a particular device will operate before
failing. MTBF ratings indicate the
sturdiness of hard disk drives and printers.
Megabit
(Abbreviated Mb.) Approximately
one million bits: 1 bit x 1,0242 (that is,
1,048,576 bits).
Megabyte
(Abbreviated MB.) (MB) A unit
of measurement approximately equal to 1
million bytes (1,048,576 to be exact).
Megahertz
A measurement of clock
cycles in millions of cycles per second.
Memory
A Term commonly used to refer to
computer system's random access memory (see
also RAM). The term memory has also been
used to refer to all types of electronic
data storage (see storage). A computer
system's memory is crucial to its operation;
without memory, a computer could not read
programs or retain data. Memory stores data
electronically in memory cells contained in
chips. The two most common types of memory
chips are DRAM and SRAM.
Memory Bank
A logical unit of memory in
a computer, the size of which is determined
by the computer's CPU. For example, a 32-bit
CPU calls for memory banks that provide 32
bits of information at a time.
Memory Configuration
The amount
of memory in an IC and how it is accessed.
Also, a code on the lot traveler used to
indicate the IC's memory configuration
(e.g., 1M1 = 1 Meg x 1, 4M4 = 4 Meg x 4,
etc.).
Motherboard
Also known as logic board, main board, or
system board; your computer's main
electronics board, which in most cases
either contains all CPU, memory, and I/0
functions, or has expansion slots that
support them.
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N
Nanosecond (ns)
One billionth of
a second. Memory data access times are
measured in nanoseconds. For example, memory
access times for typical 30- and 72-pin SIMM
modules range from 60 to 100 nanoseconds.
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O
Odd
Parity
Even parity and odd parity
are two different parity protocols used to
check the integrity of data stored in
memory. A memory manufacturer can use either
protocol in a memory product. Odd parity
adds an additional bit to every byte of data
to make the total number of 1s odd. When the
byte passes to the CPU, the parity circuit
checks the byte to be sure it is still odd.
If it is, the data is considered to be valid
and the parity bit is stripped from the
byte. If instead it registers as even, it is
considered to be invalid and a parity error
is generated.
Operating system
The program software that regulates the
operation of a computer system. Operating
systems perform basic tasks such as
input/output distribution, tracking files,
controlling peripheral devices, memory
allocation, etc.
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P
Parity
A quality control method
that checks the integrity of data stored in
a computer's memory. Parity works by adding
an extra bit of data to each byte to make
the total number of 1's either odd or even
An error is detected if the parity circuit
determines that this number has changed,
indicating that some of the data may have
been lost or otherwise corrupted. Two
different parity protocols exist, even
parity and odd parity. Parity protocols are
capable of detecting single bit errors only.
To enable multiple-bit error detection,
manufacturers must use a more advanced form
of error checking called Error Correcting
Code (ECC). See also Fake Parity.
PCB
(Printed Circuit Board) A component
made up of layers of copper and fiberglass;
the surface of a PCB features a pattern of
copper lines, or "traces," that provide
electrical connections for chips and other
components that mount on the surface of the
PCB. Examples: motherboard, SIMM, credit
card memory, and so on.
PCMCIA
(Personal Computer Memory Card
International Association) A standard that
allows interchangeability of various
computing components on the same connector.
The PCMCIA standard is designed to support
input/ output devices, including memory,
fax/modem, SCSI, and networking products.
Pipeline Burst Cache
A type of
synchronous cache that uses two techniques
to minimize processor wait states - a burst
mode that pre-fetches memory contents before
they are requested, and pipelining so that
one memory value can be accessed in the
cache at the same time that another memory
value is accessed in DRAM.
Populated Board
A PCB with components.
Power Down
To turn the system's power
OFF.
Power up
To turn
the system's power ON.
Primary
Cache
Cache that is closest to
the processor: typically located inside the
CPU chip. Can be implemented either as a
unified cache or as separate sections for
instructions and data. Also referred to as
Level 1 cache or internal cache.
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Q
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R
RAM
(Random Access Memory) A type of memory that
can be written to and read from in a
nonlinear (random) manner. When an
application is opened. it is transferred
from the hard drive to RAM where it is more
readily accessible. RAM enhances system
performance because it can process requests
from the CPU more quickly than the hard
drive. The kind of RAM used in main memory
on most computers is Dynamic RAM (DRAM).
DRAM stores data as electronic signals.
These signals must be constantly refreshed
to keep them from dissipating. The more RAM
your computer has, the more data it can
store at one time and subsequently the more
efficiently your computer will operate. The
data held in RAM is lost when the computer
is turned off. The term random derives from
the fact that the CPU can retrieve data from
any individual location, or address, within
RAM.
RAS
Row Address Select (or Strobe): a
control pin on a DRAM used to latch and
activate a row address. The row selected on
a DRAM is determined by the data present at
the address pins when RAS becomes active.
RIMM
A memory module trademarked by
Rambus that is used with RDRAM chips and has
different pin settings than a DIMM package.
Refresh
An electrical process
used to maintain data stored in DRAM. The
process of refreshing electrical cells on a
DRAM component is similar to that of
recharging batteries. Different DRAM
components call for different refresh
methods.
Refresh Rate
The speed at which DRAM is
refreshed. DRAM stores data as a series of
electron charges in individual cells. This
data must be constantly recharged or
'refreshed' to keep the data from
dissipating. The refresh rate refers to the
size of the data that must be recharged, and
is typically expressed in kilobytes (~1,000
bytes). Two common refresh rates are 2K and
4K, with 2K being the faster rate.
Registered Memory
Registers on a
memory module increase the reliability of
high-speed data access by storing the data
for one clock cycle before releasing it to
the motherboard. Registered memory is
typically employed in servers and other
mission-critical systems where the proper
management of data is exceptionally
important.
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S
SDR
See SDRAM
SDRAM
(Synchronous DRAM) A DRAM
technology that uses a clock to synchronize
signal input and output on a memory chip.
The clock is coordinated with the CPU clock
so the timing of the memory chips and the
timing of the CPU are "in synch." The
synchronization eliminates time delays and
allows for fast consecutive read and write
capability, thereby increasing the overall
performance of the computer. SDRAM has two
separate memory banks that operate
simultaneously, while one bank prepares for
access, the other is being accessed. SDRAM
allows the CPU to access memory
approximately 25 percent faster than EDO
memory because it is controlled by the
system clock. SDRAMs can only be used in
computers designed for it and cannot be
mixed with any other type of memory. SDRAM
can operate at 100MHz, 133Mhz and features a
burst mode that allows it to address blocks
of information instead of small data bits.
SIMM
(Single In-line Memory Module) A
memory package consisting of a number of
DRAM chips on a small printed circuit board.
This board provides the connection between
multiple memory chips and the computer
system. SIMMS come in various pin
configurations, the most common type being:
30 pin and 72 pin. A 30 pin SIMM has a row
of 30 tin or gold pins long the bottom of
the module which determine the amount of
data the module can handle. These pins
connect to only one memory chip as opposed
to DIMMs which can connect to multiple
chips.
SIMM Socket
An
interconnect component mounted on the system
board, or motherboard, designed to hold a
single SIMM.
SODIMM
(Small Outline Dual In-line
Memory Module) An enhanced version of a
standard DIMM. The small outline DIMM is
about half the length of a typical 72-pin
SIMM. This compact DIMM are used in mobile
computing devices. SO DIMMs come in a
variety of pin sizes and can be installed
either singly to support 32-bit systems, or
in pairs to support 64-bit systems.
Soft Error
An error caused by a
temporary disruption of the memory cell
SOJ
(Small Outline J-lead) A common form
of surface-mount DRAM packaging. It is a
rectangular package with J-shaped leads on
the two long sides of the device.
Serial Presence Detect
An EEPROM on
certain memory modules used to store and
provide information to the system using the
module.
Static Random Access
Memory
(see SRAM)
SRAM
(Static RAM) SRAM is similar to
DRAM but does not constantly refresh. SRAM
is faster and more expensive than DRAM and
is generally used for speed-critical areas
of the computer such as cache memory.
Synchronous Cache
A kind of L2 cache
that is synchronized with the CPU. This
eliminates the lag time created while the
CPU waits for cache memory to fulfill its
requests. Synchronous cache is typically 3
to 5 percent faster than asynchronous cache,
and is a full 20 percent faster than
standard DRAM. See also Asynchronous Cache.
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T
TAG
The subset of the CPU address bits used to
compare the tag bits of the cache directory
to the main memory address being accessed.
TSOP
(Thin Small Outline Package) A type
of DRAM package that uses gull wing shaped
leads on both sides. TSOP DRAM mounts
directly on the surface of the printed
circuit board. The advantage of the TSOP
package is that it is one-third the
thickness of an SOJ package. TSOP components
are commonly used in small outline DIMM and
credit card memory applications.
Type
This number (x8, x9, x32,
x36, x64, x72, x80) refers to the bit depth
of a module, or to the size of the data path
used to access the memory.
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U
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V
Vcc
Collector Common Voltage.
Volatile Memory
Memory that loses
its contents when the power is turned off. A
computer's main memory, made up of dynamic
RAM or static RAM chips, loses its content
immediately upon loss of power. Contrast
ROM, which is non-volatile memory.
VRAM
(Video RAM) VRAM has two separate
data ports. One is dedicated to updating the
image on the screen while the other one is
used for changing the image data stored in
memory. This "dual-ported" design gives
higher performance than DRAM which cannot
read and write simultaneously but is more
expensive.
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W
Write Time
Time expended from the
moment data is entered for storage to the
time it is actually stored in the memory
cell.
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X
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Y
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Z
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